Stress urinary incontinence (SUI) is a major medical problem that affects up to one third of middle aged women and has a significant impact on quality of life. A major contributing factor to the development of SUI is weakness and dysfunctional reflex activation of the muscles of the pelvic floor during times of increased bladder pressure. As with any muscle, these muscles will respond well to strengthening and re-education yet patients with SUI often find it very difficult to produce the effective voluntary contractions necessary for successful rehabilitation—due a combination of difficulty in establishing conscious control and disuse atrophy. There is a clear need for effective neuroprosthetic methodologies to facilitate effective pelvic floor contractions and promote successful rehabilitation for patients with SUI.
Previous research efforts have attempted to find effective means of using support mechanisms to facilitate pelvic floor contractions. One such method is the use of neuromuscular electrical stimulation (NMES)—a therapeutic approach that has been used in musculoskeletal rehabilitation for many years. NMES has been employed in the rehabilitation of SUI for some time now with generally positive, but mixed, results.
Since the early 1990s the most commonly used NMES method for incontinence rehabilitation is to use a vaginal or rectal electrode probe to deliver the electrical stimulation. By definition these probes are invasive and thus less appealing to many patients and clinicians. Patient comfort levels tend to be poor and the probe can also cause local tissue trauma with associated post treatment bleeding and tenderness. Whilst these invasive electrodes induce some pelvic floor contraction it is typically of limited strength; thus reducing its likely efficacy.
Current density around the area of the invasive electrode is high leading to an uncomfortable sensation for the patient, this is exacerbated by the tendency of the electrodes to fall away from the tissue. Further to this, the invasive electrodes can also cause minor tissue damage leading to further discomfort. This greatly limits the tolerance of NMES as a therapeutic approach for SUI and rehabilitation gains are often limited by poor compliance as a result.
In previous times NMES protocols for SUI were centred on use of pairs of relatively small electrodes situated over the belly and the muscle. Current flows from one to the other to produce a relatively simple electrical field in the area between the electrodes to produce the required pelvic floor contractions. However, the strength of contractions produced by these external electrode systems were generally poor and unpredictable and more recent approaches to using NMES in SUI treatment have employed an invasive approach.
There is therefore a need to develop an effective NMES treatment that avoid the need for invasive electrodes and relies instead on the use of external electrodes to produce a more acceptable and comfortable yet clinically effective treatment for SUI and other conditions.